The notion of "skill" is used in psychological literature in two contexts: first - in relation to an ability to perform a certain purposeful activity, second - in relation to an ability to perform particular acts, operations. In the latter, operational, context "skill" and "habit" are identical notions denoting possessions of a certain means to perform an act, an operation. A skill is characterized by the quality of performance and by the method of control. In the process of mastering a skill there appear wider possibilities to control its performance and to perform it automatically. Automation of acts is not a necessary feature of skills (habits). The principal feature of a skill is the quality of performance of particular acts.